What are those tube things on phantoms in Halo 3 ODST?

[Ville Fball #18]

LIke the Phantoms keep flying around with big tubes the just saw along, IDK!!!!!!!!!!!

 

[Xbox 360 FTW]

Logically, since in the mission before the last one (where you fly in a banshee) i saw one on one of those phantoms with a pod charging on the circle things. So imagine they are like an attachment to charge something or/and maybe it uses it to charge instead of fuel?
Anyway thats what i think.

 

[Nick]

im guessing its like a pod to drop off troops or something like that